A light pen for use in data imput to data processing equipment, has an adjustable tip assembly wherein the tip switch sensitivity and tactile feel or feedback to the user can be varied according to user preferences and particular applications. In one mode, the pen can be set for a normal

A cordless light pen for use with a cathode ray tube display screen as a data input for a digital computer. Contained within the exterior barrel of the pen is a depressible tip having a core made from a plastic which has been treated and whose index of refraction causes light entering in